A Bright Nova in Sagattarius

Yet another nova has been spotted in the Sagittarius. This makes the 4th nova detected in that constellation this year.

This one is a bit brighter than the others making it an easy target for small telescope users. Even small binocular observers under dark skies will be able to spot it.

Nova Sgr 2012 No. 4 (also known as PNV J18202726-2744263) is around magnitude 8.0 give or take a few tenths of a magnitude. It is very possible that the nova has already begun its decline phase and may be a bit fainter (~8.5). The nova is located at

RA = 18h 20m 27s.26   Decl = -27° 44′ 26″.3  (2000.0).

More info on the nova and how to produce finder charts can be found on the AAVSO Special Notice #289.

Nova Oph 2012 Fades Rapidly

After spending the past 3 months since discovery bouncing back and forth between V magnitude 10.5 and 12.5, Nova Oph 2012 has finally begun to fade. And what a fade! In just the past 24 hours the nova has faded by over 2 magnitudes. Over the past 48 hours the fade has exceeded 3 magnitudes.

Only a few days ago I posted (see post here) that Nova Oph 2012 was likely to be a ‘P’ or ‘plateau’ type of nova based on the shape of its lightcurve near maximum. Namely the nova spent months near maximum brightness. Well there is another type of nova described by Strope, Schaefer and Henden (2010) called the ‘D’ or ‘dip’ type. D-types experience a large sharp drop in brightness due to the formation of a dust shell around the nova which absorbs the light of the nova. As a result, less light gets through the dust and it appear fainter to us. Over time the dust clears and the nova starts to brighten again. Is Nova Oph 2012 a ‘D’ type. I’m certainly not a nova expert but for now we’ll just have to watch what other tricks this nova has up its sleeves.

Lightcurve of Nova Oph 2012. Plot includes visual and CCD V magnitude measurements. Observations overplotted with a cross were made by Carl Hergenrother. All observations are from the AAVSO. Plot created with the AAVSO Variable Star Plotter (VSP).

Novae Update

There are now 4 (and possibly 5) novae in the Sagittarius/Ophiuchus/Scorpius region that have erupted in the past few months. Three of the 5 are still bright enough for small telescope observers.

I have been routinely observing all 5 with the Sierra Stars Observatory 0.61-m telescope. Continuing the post, 3 Relatively Bright Novae in Sagittarius/Ophiuchus, from last month, here is the latest on the novae.

Nova Sagittarii 2012 = PNV J17452791-2305213

Nova Sag 2012 has rapidly faded from its peak magnitude of V ~ 8.8. Recent CCD observations place it at V ~ 15.2 and much too faint for most visual observers. This nova is typical of most novae with a sharp peak in brightness and rapid fading. Novae are classified based on the shape of their lightcurve and the rate at which they fade. This nova faded by 2 magnitudes (t_2) in about 3 days, by 3 magnitudes (t_3) in about 6.5 days and 6 magnitudes (t_6) by about 40 days. According to the Strope, Schaefer, Henden (2010) classification scheme, Nova Sag 2012 appears to be either a S(6) or O(6) type nova. S types display smooth declines in brightness while O types show oscillations in the lightcurve. You can see hints of rapid oscillations of up to 1 magnitude during the month of May. The ’6′ in each classification is the length of time for the nova to drop 3 magnitudes in brightness. In this case, the nova dropped 3 magnitudes from magnitude 8.8 to 11.8 in 6-7 days.

 

Nova Ophiuchi 2012 No 2 = PNV J17395600-2447420

Similar to Nov Sag 2012, Nova Oph 2012 No 2 also faded rapidly from a peak of ~11 to ~15.2. Assuming the earliest observations represent it maximum brightness, it faded 2 magnitudes (t_2) in 7 days and 3 magnitudes in (t_3) in 15 days. Its smooth decline makes it a S(15) nova. There was a slight brightening starting on June 14 that lasted till June 20. This could be what’s called a ‘cusp’ which is typical of the C or cusp type of nova. Usually these cusps are larger and longer lasting so the S(15) classification still seems the best for this nova.

The brightness graph below shows observations taken in 3 wavelengths, V for visual or yellow, B for blue and R for red. It is apparent that the nova is red since it is brightest in the R filter. Part of this is that much of the nova’s light is due to Hydrogen-α emission which is located at a wavelength covered by the R filter.

 

Nova Ophiuchi 2012 = PNV J17260708-2551454

In contrast to the 2 novae above, Nova Oph 2012 is a much slower nova. For starters the nova was first seen ~3 months ago and it still hasn’t faded by 3 magnitudes. Also it has shown numerous oscillations of almost 2 magnitudes. Currently around magnitude 12.8, the nova did appear to start fading but that fading is in question since the nova has actually brightened a little over the past week. There is a type of nova called ‘Flat’ or F types due to their long flat maximas. Nova Oph 2012 may be of this type. Only time (and more observations) will tell.

 

Nova Scorpii 2012

Now on to the first of the more recently discovered novae. Nova Scorpii 2012 may go down as an historic nova. The Microlensing Observations in Astrophysics (MOA) collaboration were observing the region of the sky around Nova Sco 2012 as part of their program to detect and study microlensing events (the brightening of foreground stars by lower mass objects passing between the star and Earth). An otherwise unassuming 19th magnitude (in the I band) star started a slow rise in brightness between May 14 and 16. The rate of brightening started to increase on May 24. Soon a 1.6-hr oscillation (due to the rotation period of the nova double star system?) was observed superimposed on the brightening trend. Suddenly on June 1 to 2 the object jumped 6 magnitude in brightness. Spectroscopic observations confirm the object as a slow “Fe-II” nova. Never before have the earliest days of a classical nova outburst been observed.

The nova peaked around V magnitude 9.9-10.0 on June 20. Since then it has faded to V magnitude 10.8. It is located a few degrees north of the bright open star cluster M7 at R.A. = 17h50m53s.90, Decl. = -32d37’20″.5 (equinox 2000.0).

PNV J17522579-2126215

The newest “nova” is still a ? since there hasn’t been any published spectroscopic observations confirming its nature. It was discovered by K. Itagaki with an independent discovery by Y. Sakurai (both of Japan) on June 26. I was able to observe it last night with the Sierra Stars 0.61-m at V = 9.8. The “nova” is located a few degrees to the NW of M8 at R.A. = 17h52m25s.79 Decl. = -21d26’21″.5 (J2000.0).

3 Relatively Bright Novae in Sagittarius/Ophiuchus

Hello Everyone!

First a quick update. A few months back I moved to a new home here in Tucson. During the move I had to take down my meteor camera set-up. Though it took me longer than it should to find the time to set the cameras back up again, I finally did get around to it. BUT… all four of my cameras (the 3 PC164Cs and the single Watec 902H2) now have issues. One of the PC164Cs is completely dead (no signal, nasty electrical burning smell). The other three cameras produce a very noisy (and suspiciously similar) signal. I was hoping it was related to my cables/connectors but my all-sky Sentinel system works fine. Hopefully I won’t have to buy a new camera. In the meantime, my video meteor watching remains on hold.

In the meantime I’ve been remotely observing a number of recently discovered novae. The most recent nova is Nova Ophiuchi 2012 No. 2 (originally designated as PNV J17395600-2447420). This nova was first spotted by John Seach of Chatsworth Island in New South Wales, Australia on May 19.484 UT at magnitude 10.5. Seach was hunting for novae with a DSLR camera and 50mm f/1.o lens. Spectroscopic observations reported on CBET 3124 classify the nova as a Fe II-type.

I have been observing the Nova Oph 2012 No 2 remotely with the Sierra Stars 0.61-m on an almost nightly basis. After peaking around V magnitude 10.5, the nova has now faded to V ~ 13.4. In the red (R-band) it is nearly 2 magnitudes brighter. Part of the reason for the extreme red color is that the nova is located behind a dust-rich area of the galaxy. Dust can redden any starlight that passes through it. The difference between the nova’s brightness in the V and R bands also appears to be increasing. This is probably due to actual changes in the light of the nova rather than intervening dust.

Nova Sagittarii 2012 (originally designated as PNV J17452791-2305213) was picked up by Russian astronomers, Stanislav Korotkiy and Kirill Sokolovsky, on Apr. 21.011 UT at magnitude 9.6. They used a 135-mm f/2 telephoto lens and ST-8300M CCD camera. In the over one month since maximum, the nova has faded from V ~ 8.9 to V ~ 14.5.

While the two novae above are behaving like ‘normal’ nova with rapid and gradual fading, the first nova of 2012 to be found in Ophiuchus is acting much differently. Nova Ophiuchi 2012 No. 1 (originally PNV J17260708-2551454) was yet another John Seach find. He originally reported the nova on Mar. 23.39 UT at magnitude 9.2. Since that time the nova has widely varied in brightness from as bright as V ~ 10.5 to as faint as V ~ 12.5. Even over the course of hours V-band photometry shows brightness changes of many tenths of a magnitude.

As the two novae above show, most novae fade rather rapidly. Nova Oph 2012 No. 1 hasn’t faded much in two months. It will be very interesting to see how its lightcurve develops. Will it finally start fading? Brighten again to a brighter maximum? Will its brightness jitters continue? Stay tuned…

In case your wondering, the PNV J########-####### style designation is a preliminary designation given to suspected novae and supernovae by the Central Bureau of Astronomical Telegrams. The PNV stands for possible nova. PSN would mean possible supernova. The numbers after the J is the Right Ascension and Declination of the suspect. So PNV J17260708-2551454 means ‘a possible nova at Right Ascension of 17h 26m 07.08s and Declination of -25° 51′ 45.4″.

Lightcurves for all three novae were produced on the AAVSO website.

The Ups and Downs of T Pyx

Let me just say that I really like this star. On the evening of May 7th UT (6th in local time) I measured T Pyx at magnitude 6.8. This was just a tenth of a magnitude brighter than a convenient magnitude 6.9 star located nearby. The next night I was expecting to find T Pyx even brighter but was surprised to find it fainter than the nearby reference star. After a break of a few days I wasn’t sure what to expect but I was pleasantly surprised to find T Pyx has brightened yet again. My observations placed it as magnitude 6.5.

If all goes according to predictions based on its 1966 outburst, the nova should brighten by another few tenths of a magnitude during the next week or so. Then begins its long fade back to quiescence.

Visual and CCD magnitude measurements for T Pyx. Credit: AAVSO.

T Pyx Fading?

This evening I took another peak at T Pyx and was surprised to find it looking a bit fainter than it did last night. The lightcurve from the AAVSO suggests that T Pyx may have been slowly fading over the past 3 days or so. It will be interesting to see if this is a short-term dip before brightening to its predicted peak later this month, or if this is the beginning of a fade back to quiescence.

Visual and CCD V lightcurve for T Pyx from the AAVSO LightCurve Generator. Credit: AAVSO.

T Pyx Brightens Again

Last time we talked about the nova T Pyx it was holding steady around magnitude 7.4 and 7.7. Over the past few days T Pyx has resumed brightening and it currently around magnitude 6.7 to 7.0. If it continues to do as it did in 1966, it should brighten to around magnitude 6.3 over the next 3 weeks.

T Pyx Update

I estimated the brightness of T Pyx at magnitude 7.3 during the past 2 evenings. This is a bit on the bright side with most observers placing it between 7.3 and 7.6. T Pyx should continue to slowly brighten for the next few days before entering a phase of more rapid brightening that should ultimately bring it to a peak magnitude of ~6.3.

Visual magnitude estimates submitted to the AAVSO. My observations are denoted by the blue crosses. Plot produced with the AAVSO Variable Star Plotter. Credit: AAVSO.

T Pyx’s Slow and Steady Brightening

Recurrent nova T Pyxidis continues to slowly brighten in the southern evening sky. The digital camera image below was taken by Bob Lunsford through a Celestron C9.25 schmidt-cassegrain telescope. T Pyx is the bright, slightly bluish star just to the lower right of center.

Image of T Pyx (2011 April 16 UT) and the surrounding star field with a C9.25 telescope and Canon PowerShot S2 camera. T Pyx is the bright bluish star near the center. Credit: Bob Lunsford.

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After rapidly brightening from a faint 15th magnitude to 8th magnitude in only 2 days, T Pyx’s rate of brightening has substantially slowed down. Over the past ~5 nights the nova has only brightened by an additional ~0.5 magnitudes. Last night I used 10×50 binoculars to estimate it at magnitude 7.5.

If T Pyx behaves as it did during its last outburst in 1966 it’s brightening trend should stop during the next few nights. Then for the next week or so its brightness will remain constant. After this short pause, the brightening trend will resume with an estimated peak around magnitude 6.3 in mid-May. That’s of course, if the nova follows the same playbook as it did in 1966 which is not a given.

Visual lightcurve based on visual observations submitted to the AAVSO. Credit: AAVSO.

T Pyxidis Erupts

For the first time in nearly 45 years, the recurrent nova T Pyxidis is in outburst. The usually quiescent 15th magnitude star has rapidly brightened to around magnitude 7.5 to 8.0. If it behaves similar to previous outbursts a further brightening to around magnitude 6.4 should occur over the next month.

Novae are the result of a thermonuclear explosion caused by the buildup of hydrogen on the surface of a white dwarf. As members of a double star system, the hydrogen is stripped from a normal main-sequence star unto the white dwarf. After each explosion it takes some time for the hydrogen to build up again in order to create the next nova outburst. The recycle time can be on the order of thousands to millions of years. A rare class of recurrent nova experience outbursts much more frequently (on the order of tens of years). The shorter outburst interval is due to the white dwarf being near the Chadrasekhar mass (the mass at gravity wins out and a white dwarf would collapse in a Type Ia supernova) and a high rate of hydrogen transfer between the stars.

On April 14, amateur astronomer Mike Linnolt of Hawaii spied T Pyxidis at magnitude 13. Though faint, this was a full 2 magnitudes brighter than usual and a clear sign that a new outburst had begun. Over the next 2 days, the nova rapidly brightened and many observers (including myself and friend of the blog Salvador Aguirre) are currently placing it at magnitude 7.8 (give or take a few 0.1 mags).

Visual lightcurve for recurrent nova T Pyx. Credit: AAVSO.

According to Dr. Bradley Schaefer (Louisiana State University) the nova should slowly brighten further over the next month and become as bright as magnitude 6.4 by May 20. This is based on previous outbursts of T Pyx. More can be found from Dr. Schaefer at the AAVSO website.

The current outburst is the 6th observed outburst by T Pyx. The previous 5 having occurred in 1890, 1902, 1920, 1944 and 1967. An earlier outburst from around 1866 is surmised by debris observed by the Hubble Space Telescope. There have been predictions that the rate of material collecting on T Pyx is slowing down and future outbursts will occur at longer intervals and might even stop for an extended period of time.

T Pyx is located in the faint southern constellation of Pyxis (the mariner’s compass) at a declination of -32°. This makes the star a difficult object for northern observers. Even when if it reaches 6th magnitude it will be a binocular or small telescope object for most observers.

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